Car won't start: Codes, Causes & Fixes
First tell the two cases apart: if the engine does not crank at all, the battery, battery terminals, starter or a security/immobilizer lockout are the usual suspects; if it cranks but won't fire, look at fuel delivery, crankshaft position sensor and ignition. Codes such as P0335 (crankshaft sensor) or immobilizer messages narrow it down, but a no-crank fault may leave no code at all. Check battery voltage and terminal connections before anything else.
123Codes
3.2Average severity
28%High or critical
21%DIY-friendly
Severity distribution
Most viewed
P0093
Powertrain
Rail pressure is dropping faster than injection explains: fuel may be escaping. Stop and check…
Critical
P0216
Powertrain
The ECU can't control or confirm injection timing, usually on a diesel with an electronic…
High
P0001
Powertrain
The PCM can't drive the solenoid that meters fuel into the high-pressure pump. Often a no-start…
High
P0192
Powertrain
The rail pressure sensor signal voltage has fallen below the lowest value a working sensor can…
Moderate
P0090
Powertrain
The engine computer sees an electrical fault in the wiring or coil of the fuel pressure control…
Moderate
P0562
Powertrain
The engine computer sees too little supply voltage – usually a charging, battery or ground…
Moderate
All codes (35)
U0105
Network
The PCM lost contact with the separate module that fires the injectors, common on diesel…
High
U0109
Network
The PCM lost contact with the module that controls fuel pump speed; stalling or no-start can…
High
U0110
Network
The hybrid/EV system lost contact with the module that runs electric drive motor A.
Critical
U0115
Network
Modules lost contact with the second engine computer on vehicles that use two of them.
High
U0404
Network
The electronic shifter reports a lever position the transmission can't trust, so Park may not…
High